14 



PANAMIC DEEP SEA ECHINI. 



reach the actinal system in all the interainbulacra, but all greatly reduced 

 in size. There are in this stage four rows of buccal plates, thirty-three 

 ambulacral and eight pairs of interambulacral plates, with a ninth in the 

 odd interambulacral area ; not only the seventh pairs of the preceding stage 

 but the eighth have become fully developed, and the ninth are indicated. 



IS 



35 mm. 

 FlO. 34. POROCIDARIS C'OBOSI. 



Ill a specimen of 21 mm., Fig. 33, there are thirty-six to thirty-eight 

 pairs of ambulacral and eight to nine of interambulacral plates, with four 

 rows of buccal plates, the plates at the actinal system being in about the 

 same stage of resorption as the preceding stage. 



In a specimen of 35 mm., Fig. 34, with six and seven rows of buccal 

 ])lates, there are fifty-si.\, fifty-seven and fifty-eight ambulacral plates, with 

 ten pairs of interambulacral plates, and one plate of the eleventh in the 



